Fluid pressure braking system



Oct.13, 1942. v H. c. 'B'OWEN' 2,298,856

FLUID PRESSURE BRAKING SYSTEM Original Filed Sept. 20, 1937 g I ft-25327 CBOWEN ATTORNEY.

Patented oct. 13, 1942 V UNITED "STATES PATENT ,OFFICE 2,298,856 PRESSURE BRAKING SYSTEM Herbert C. Bowen, Detroit, Micln, assignor to Hydraulic Brake Company, Detroit, Mich, a corporation or California Original applicationseptember 20, 1937, Serial No. 164,636, 110w. Patent No. 2,201,518, dated November 21,. 1939.

v pending application, Ser. No. 164,636, filed Sept. 20, 1937, now Patent No. 2,201,518 issued November 21, 1939, and is made in accordance with requirements of the United States Patent Oilice under provision of Rule 42.

' An object of the invention is to provide a fluid pressure braking system including a fluid pressure producingdevice operative to maintain a predetermined pressure on the fluid in the syste so as to exclude air fromthe system.

I braking system embodying the invention; and

Fig. 2, is a vertical sectional view of the fluid pressure producing device.

, f Referringto the drawing for more specific details of the invention, In represents a fluid reservoir having a filling opening l2 normally closed as by a plug l4 having openings [6 therethrough for venting the reservoir to the atmosphere.

-A fluid pump I8 in the bottom of the reservoir includes a cylinder 28 having one of its ends opening through the wall of the reservoir and closed as by a head 22, and its other end closed by a head 24 having a port 26 providing a communication between the cylinder 20 and the reservoir, and a-valve'28 is seated on the head 24 for control of theport 26. The cylinder. 20 also has in its wall a port 38 providing another communication between the cylinder and the reservoir.

A piston 32 reciprocable in'the cylinder 28 between the ports 26 and 30 has on its head a sealing cup '84, and a light spring 36 interposed between the, cup 34 and the valve 28 serves to retain the valve and cup against displacement. A rod 38 attached to the piston extends through'an opening in the head 22 of thecylinder and terminates in a clevis '48. A sealing washer 42 sleeved on the rod and seated on'the head 22- of the cylinder inhibits seepage of fluid fromv the cylinder past the rod, and a spring 44 sleeved over the rod between'the sealing washer 42 and the back or the piston 32 serves to retain thewasher Divided and this application December 14,1939, Serial No. 309,251

or against displacement and also to impose a predetermined load on the piston 12 commensurate with the pressure desired on the fluid in the system.

A cylinder 46 depending from the bottom of the reservoir has one of its-ends open and its other end closed as by a head 48 provided with a dis-;

charge port 50, and arranged in the wall of the cylinder are spaced ports 52 and .54 providing communications between thecylinder 46 and c the cylinder 28 of the fluid pump.

A fluid pressure delivery pipe or conduit 56 connected to the discharge port 50 has branches connected respectively to fluid pressure actuated motors 58, preferably arranged in pairs, one pair for actuating brakes associated with the rear wheels of a motor vehicle, andianother pair for actuating brakes associated with the front wheels of the vehicle. r The brakes may be of conventional type. As

shown; each brake includes a fixed support or backing plate 68, a rotatable drum 62 associated with the backing plate, a pair of corresponding friction elements or shoes 54 mounted on the p backing plate for cooperation with the drum, a

retractile spring 65 connecting the shoes, and a unotor corresponding to the motors 58 mounted on the backing plate between the shoes and operative to actuate the shoes into engagement with the drum against the resistanceof the retracti spring. a I

A piston 68 reciprocable in the cylinder 46 is held against displacement by a retaining ring III seated in a groove in the wall of the cylinder adjacent the open end of the cylinder. The pis ton 68 includes a head 12,- a skirt" supporting a sealing cup 16 for inhibiting'seepage of fluid from the cylinder past the piston, and a reduced body portion 18 providing in conjunction with the wall of the cylinder an annular chamber 88 communicating with the cylinder 20 of the fluid pump as by way of the port 52.

The head of the piston 68 has a plurality o passages 82 therethrough providing communications betweenthe annular chamber 88 and that portion of the cylinder forward of the. piston 68. A sealing cup 84 on the head of thepiston 68 controls the passages", and a spring 86 interposed between the cup and the head 48 of the cylinder serves to retain the cup against displacement-and also to return the piston to its retracted position.

A recess 88 in the back or the piston 68 receives one end of a thrust rod 88. Therod has suitably securedthereon a flexible boot 92 connected to the opeaend of the cylinder for the I02. to theclc'vis 94 on the thrust rod 90, and a lug i [04 on the foot pedal lever is attached to one ,e'nq of alinkl06 ,by"an overrunning connection |08,'and'the other end-of the link I6 is pivthe resistance of the retractile springs tively retard rotation of'the drum.

and on the other end'ofthe thrust rod is a clevis 9 4 'A ,foot pedallever 96 of conventional type is rockably mounted on a stubshaft 33 and connected by a retractile spring-100 to a flxed support The foot pedal lever is pivotally connected otally connected to the .clevis 40 on the piston I rod 38 of the fluid pump l8.

In a normal operation, upondepressing the foot pedal lever 96,- force is transmitted therefrom through the thrust. rod 90 to the piston 68, resulting in movement of this piston on its compression stroke. During the initial movement of the piston, the cup 84 on the head of the piston covers the port 54, and, thereafter, as the piston advances on its compression stroke, fluid in the cylinder 45 forward ofthe piston is displaced therefrom through the discharge port 50 and the ;fiuid pressure delivery pipe'5li and its branches into the fluid pressure actuated motors 58 connected between the friction elements of the brakes. 'This results in energi'zation of the motors and the consequentactuation of the friction elements intoengagement with thedrums against to effec- Upon concluding a braking-operatiomthe foot pedal lever 96 is released and-is returned to re.-

- tracted .positionunder"theinfluence of the retractile spring 100.. This movement of the foot pedal lever retracts the thrust pin 90 and releases the piston 68, whereupon the spring 86 becomes efiective to return the piston to its retracted position.

As the piston 68 returns to itsretracted posi- Ition, a partial vacuum is created-in the cylinder 46 forward of the piston. This results in drawing fluid from the pump cylinder 20, through the exclusion of dust and other foreign substances,

' of that required to maintain a desired pressure on the fluid in the system, the piston 32 is moved against the resistane'of the spring 44 to uncover the port 30 so that a portion of the fluid may be returned to the reservoir.

While this invention has been described in connection'with certain specific embodiments, the

' principl invo'lve'd is susceptible of numerous other applications that'will readily occur to persons skilled in the art. The invention is, therefore, to be limited only as indicated by the scope of the appended claims.

Having .thus described the various features of the invention, what I claim as new and desire to secure by Letters Patent is:

1. In a fluid pressure braking system including a reservoir,'a fluidpressure producing device supplied therefrom and means for actuating the device, a pump in the reservoir below the fluid port 52, into the annular chamber .80, thence. through the p ssages 82 inthe head of the piston 68, past the cup 84 on the'head of the piston,

- into that portion of the cylinder forward of the piston, completely filling the cylinder. This may result in a slight movement of the piston 32 of the pump under the influenceof the spring 44, due todisplacement of fluid from the pump cylinder 20. However, during this period, fluid is returning to the cylinder 46 from the fluid pressure actuated motors and the fluid pressure delivery piping ,s'ystem connecting the motors to thecylinder under the influ ence'of the .retractile springs connected'between the friction elements of the respective brake structure's. Accordingly,

the'pressure on the fluid in the system 'is maintained fairly constant.

Should there occur a drop in the pressure on the fluidin the system, the piston '32 of the-fluid level including a chamber having, an inlet communicating with the reservoir and outlets in continuously open communication with the pressure producing device, a piston reciprocable in the chamber, a spring imposing a load on the piston, and means connecting the piston to the actuating means including an overrunning connection for automatically operating the piston to maintain a positive pressure on the fluid in the system, said v inlet controlled by a valve in the pump chamber spring-loaded by the piston to normally inhibit passage of fluid therethrough.

2. In a fluid pressure producing device comprising a reservoir, a cylinder associated therewith, a piston movable in the cylinder for creating pressure, an actuator for the piston, a pump in the base of the reservoir including a chamber having an inlet communicating with the reservoir and outlets communicating respectively with the cylinder and the reservoir, a spring-loaded piston reciprocable in the chamber controlling the outlet communication between the pump and reservoir, a spring-pressed valve in the pump chamber for controlling the inlet communication of the chamber, the outlet communication between the pump and cylinder being continuously open, and-means including an overrunning connection for coupling the actuating means;to the piston reciprocable in the chamber for' operation thereby when the pressure on'the fluid-in the predeteremined degree.

device drops below a HERBERT C. BOWEN. 

